Problem: $\dfrac{8}{5} - \dfrac{9}{12} = {?}$
Answer: $ = {\dfrac{8 \times 12}{5 \times 12}} - {\dfrac{9 \times 5}{12 \times 5}} $ $ = {\dfrac{96}{60}} - {\dfrac{45}{60}} $ $ = \dfrac{{96} - {45}}{60} $ $ = \dfrac{51}{60}$